Spotify is an ad-supported online music-streaming service that allows users to search through a catalog of millions of songs. The service launched in the U.S. last July and made news when Facebook singled out Spotify as an example of "frictionless sharing."

Facebook members who choose to link their accounts to Spotify can broadcast their playlists or songs to their friends on the social network. There is anoption to select private listening, however.

The new Spotify Play Button is similar to a stand-alone widget, with one caveat: You must have Spotify installed on your computer to stream the music.

So how exactly does it work? When you click the play button, the widget will launch the Spotify desktop client on your computer. The song will play simultaneously on both the website and Spotify.

To create the a Spotify Play Button, right click the song or playlist you want to share in Spotify, select "Copy Spotify URI." Then head over to the Spotify developer site to generate an embed code that can be pasted any blog or website.

Once finished, the Spotify Play Button should look like the example below.

There are currently about 3 million Americans on Spotify, with about 600,000 paying members.